"Once Upon a Time" introduced Elizabeth Mitchell as the Snow Queen during this past Sunday's episode of the fourth season, "White Out," which followed the introduction of characters from Disney's "Frozen" in the premiere, "A Tale of Two Sisters." Princess Anna and Elsa, the queen of Arendelle who possesses cryokinetic powers, are now series regulars.

The forthcoming episode, "Rocky Road," promises mounting ice-related drama as an icy spell is cast on Marian (Christie Laing), and residents of Storybrooke blame Elsa, unaware that the villainous Snow Queen, who runs the ice cream parlor, has the same powers as Elsa and is trying to frame her.

The plot thickens like ice this season. The second episode featured Elsa building an ice fortress around Storybrooke. She does this after she discovers Anna's necklace at Rumpelstiltskin's pawn shop and decides to trap the town in until her sister, Anna, is found. This causes the town to lose power and forces Emma to investigate. Then, the massive wall nearly freezes Emma to death when Elsa traps them both inside.

Elsa continues to demand that her sister be brought to her. And David commandeers the staff of the local butcher shop, run by Bo Peep, in order to locate Anna. As Emma slowly freezes, she's able to encourage Emma to create an exit within the wall, allowing Emma to leave.

A flashback to the Enchanted Forest shows Anna has met David when he was a lowly shepherd with a shaggy mane and before he becomes Prince Charming. Anna's fiancé, Kristoff, sent her to David, expecting that he would help Anna as she sets out on an adventure to find out what happened to her parents. But, David has problems of his own, as he's visited by the swindler Bo Peep, who demands payment. Anna encourages David to stand up to Bo Peep and be brave, and she trains him in sword fighting. Then, trouble arises when Bo Peep kidnaps Anna.

No fear. David's newfound combat skills help him to resolve the issue, forecasting David's future as Prince Charming. Anna soon leaves the farm and continues on her quest. Next on her agenda: Pay Rumpelstiltskin a visit. But the big question is, where is she now?

Watch Once Upon a Time Season 4, Episode 3, "Rocky Road," Sunday, Oct. 12, at 8 p.m. ET on ABC.